Cytological features of myxomatous fibroadenoma of the breast

Abstract

Fibroadenoma (FA) is a benign tumor that must be differentiated from carcinomas. FAs often exhibit myxedematous changes (myxomatous FA, M-FA). We previously reported on the clinical significance of M-FA. M-FA and (mucinous) carcinoma share clinical findings, rapid growth and a relatively large size, a high-depth/width (D/W) ratio, a relatively round shape, and posterior echo enhancement with internal hyperechogenicity on ultrasonography (US). Next, a biopsy is required for differential diagnosis. In this study, we evaluated the diagnostic significance of the cytological findings of M-FA with US findings. Among 13 FAs that were diagnosed by cytology, we compared (i) a group of six mucinous carcinomas with acellular mucin and a D/W ratio ≥ 0.7 (a suspicious factor for malignancy) with a group with a D/W ratio of <0.7, and (ii) the frequency of metachromasia on Giemsa stain between M-FAs and non-M-FAs among eight FA cases confirmed by histology. (i) FA lesions (7 of 13) showed metachromasia with Giemsa staining significantly more frequently than did mucinous carcinoma (0/6) (Fisher's exact test, P < 0.044). FA lesions with a D/W ratio ≥ 0.7 (6/7) showed metachromasia significantly more frequently than did FA with a D/W ratio <0.7 (1/6) (Fisher's exact test, P < 0.029). Among eight FA cases confirmed by histology, M-FA cases (6/6) demonstrated metachromasia significantly more frequently than non-M-FA cases (0/2) (P < 0.036). M-FA cytologically exhibits marked metachromasia on Giemsa staining. Combining cytological examination and understanding the clinical features of M-FA may allow us to choose cytological examination as a first-line diagnostic method for tumor-forming lesions.

Pitfalls in cytological diagnosis of mucinous carcinomas of breast

“…On cytological examination, M-FA can be differentiated from carcinomas based on the absence of marked nuclear atypia and metachromasia in the mucus components, a useful features which is seen on Giemsa staining. 3,14 Mixed tumors (invasive ductal carcinoma with mucinous component) generally yield cellular smears which on cytology show pleomorphism which is marked, necrosis and relatively small amount of background mucin. Features on cytology indicative of a mixed tumor include one or more smears totally without mucin, or scanty amounts of mucin or necrosis.…”

Diagnostic accuracy of fine-needle aspiration cytology of the breast in Japan: Report from the Working Group on the Accuracy of Breast Fine-Needle Aspiration Cytology of the Japanese Society of Clinical Cytology

“…Regarding false-positive cases, the histology of most cases was papilloma, fibroadenoma, fibrocystic disease (mastopathy) or adenomyoepithelioma. Papilloma is one of the most difficult histologic types for cytological diagnosis (19), while fibroadenoma is often misread for hyperplastic epithelial cells (20). Interestingly, adenomyoepithelioma showed the same rate of false-positive cases, for which the histological type has benign to malignant potential and is generally considered a benign lesion (21).…”

Myxomatous fibroadenoma of the breast: correlation with clinicopathologic and radiologic features

“…The present study suggests that understanding the clinicopathologic features (including the US findings of M-FAs) may allow us to avoid needle biopsies or surgical biopsies in some cases of tumorforming lesions. The cytological examination could be helpful to distinguish these cases as a first-line diagnostic procedure [7].…”